Evidence for warming of Atlantic water in the Southern Canadian Basin of the Arctic Ocean: Results from the Larsen‐93 Expedition

Abstract

Potential temperature (θ) and salinity (S) data obtained along the perimeter of the southern Canadian Basin north of the East Siberian Sea in 1993 aboard the CCGS Henry Larsen show higher temperatures in waters of Atlantic origin than in available climatological data for the Canadian Basin. In particular, a front is observed near the Mendeleyev Ridge which separates the cooler Atlantic waters of the Canada Basin from the warmer Atlantic waters observed in the Makarov Basin. The front is further characterized by a change in the θ/S slope of Arctic thermocline water, and by thermohaline intrusions (θ and S reversals) within the Atlantic layer. The idea that this warm variety of Atlantic water has come recently from the Eurasian Basin is supported by its higher level of the tracer CFC‐11.

The Arctic Ocean—a Canadian perspective from IPY

“…Although 230 Th-enriched water had reached 72.5°N in the southern Beaufort (station KC2700) in 2007 it had not spread further south. By 2009, 230 Th was high in Atlantic water south to the shelf edge, a signal synchronous with warmer Atlantic water penetrating the same area after 2002 (Carmack et al 1995;Shimada et al 2004). Together these signals are consistent with warmer Atlantic water arriving from the Alpha Ridge, which implies a change in mid-depth circulation from the normal cyclonic path-a long trajectory from Fram Strait-to an anti-cyclonic one-a shortcut.…”

An Arctic Basin Observational Capability Using AUVs

“…The recently prepared digital atlas of Russian hydrographic data (Environmental Working Group, 1997) confirms that no temperatures greater than 1°C were observed during numerous investigations between 1950 and 1989. The warming of the Atlantic layer has alsobeen reported by other investigators: Carmack et al (1995), McLaughlin et al (1996), Mikhalevsky et al (1995), and Mikhalevsky et al (1996). These observed differences represent a fundamental change in the Arctic and it is of utmost importance that these changes in the Arctic Ocean be studied in detail.…”

“…This is indicated by the increased coverage of the warmer Atlantic water that has been observed in recent years. Data collected during the cruises of the USS Pargo (Morrison et al, 1998) and the Henry Larsen (Carmack et al, 1995;McLaughlin et al, 1996) and the Summer 1994 Arctic Ocean Section of the Polar Sea and the Louis St. Laurent all indicate that the boundary between the eastern and western halocline types now lies roughly parallel to the Mendeleyev Ridge. In terms of longitudinal coverage, this means the area occupied (Morison et al, 1998) Gorshkov (1983) and Treshnikov (1977) give no indication of such warm cores and show a temperature over the Lomonosov Ridge nearly 1°C colder.…”

Comparing modeled streamfunction, heat and freshwater content in the Arctic Ocean

“…The timeseries run AWI-98 does not show this intense cooling. In contrast, it very well represents the warm water inflow, that has been observed in the early nineties (e.g., Carmack et al, 1995;Swift et al, 1997;McLaughlin et al, in press). An extremely cold state is also reached in the NYU-c run, where, as for AWI-c, the wind forcing is based on ECMWF analyses (1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993).…”